Chapter 5: ACS Data Analysis 5.1 Photometry 5.1.1 Photometric Systems, Units, and Zeropoints 5.1.2 Aperture and Color Corrections 5.1.3 Pixel Area Maps 5.1.4 PSF 5.1.5 CTE 5.1.6 Red Leak 5.1.7 UV Contamination 5.2 Astrometry 5.2.1 Coordinate Transformations 5.2.2 Absolute and Relative Astrometry 5.2.3 Impact of Guide Star Failure 5.3 Polarimetry 5.3.1 Absolute Calibration 5.3.2 Instrumental Issues 5.3.3 Flats 5.3.4 Polarization Calibration 5.4 Coronagraphy 5.4.1 Flat Fielding 5.4.2 PSF Subtraction 5.4.3 Photometry 5.4.4 Ghosting 5.5 Ramp Filters 5.5.1 Introduction 5.5.2 Existing Ground Calibrations 5.5.3 In-flight Calibrations 5.6 Spectroscopy with the ACS Grisms and Prisms 5.6.1 What to Expect from ACS Slitless Spectroscopy Data 5.6.2 Pipeline Calibration 5.6.3 Slitless Spectroscopy Data and Dithering 5.6.4 Extracting and Calibrating Slitless Spectra 5.6.5 Accuracy of Slitless Spectra Wavelength and Flux Calibration